The skin is an external organ of the body constantly subjected to attacks from the external environment, such as solar radiation, atmospheric pollutants, and the like.
These external factors, but also the gradual decline in the various functions of the body during ageing, contribute to an accumulation of damaged cell components (nucleic acids, lipids, proteins), the removal and/or the repair of which should be carried out by the cell.
The formation of damaged cell components takes place mainly via reactions involving reactive oxygen entities, such as the superoxide anion, hydrogen peroxide or the hydroxyl radical. Other reactions involving the attachment to macromolecules of glucosides or aldehydes resulting from lipid peroxidation also contribute thereto (Friguet B. Le vieillissement moléculaire et cellulaire et ses futures enjeux [Molecular and Cell Ageing and its Future Challenges], Mécanismes biochimiques).